Plenty of Fish in the Sea? Think Again.

Vegetables aren't the only things on your dinner plate that can get greener. Modern fishing practices have left 90 percent of the world's stocks depleted, according to "The End of the Line: How Overfishing Is Changing the World and What We Eat" by environmental journalist Charles Clover (The New Press, 2006).

Besides the obvious problem of catching fish faster than they can reproduce, other species, including turtles and dolphins, often get caught in nets. For every pound of shrimp harvested, 10 pounds' worth of other species are thrown away even if they're edible, according to Conservation International. Some industrial fishing methods involve indiscriminate scraping of the sea floor, causing physical damage to habitats and species.

Fish farming is an alternative but is a mixed bag: Though many aquaculture systems are wisely managed for the health of the fish population and the ecosystem, many others aren't.

The problem isn't just a global one; it's also local: The Chesapeake Bay Foundation's 2006 "State of the Bay" report gave the ecosystem's health a grade of D. Because of overfishing and pollution, oyster and crab populations are alarmingly low, while the rockfish population, which made a comeback after being nearly depleted in the 1970s, shows signs of being threatened again.

Still, you don't have to forgo fish altogether. You just have to make smart choices: Whether you're damaging the planet depends largely on where the fish comes from and how it was raised. Here, a few tips to guide you through the murky waters:

Download a comprehensive pocket guide from California's Monterey Bay Aquarium at http://www.mbayaq.org/cr/seafoodwatch.asp. The guides are organized by region (a national version is also available) and updated annually.

Look for a certification symbol from the Marine Stewardship Council on the packaging of any fish at the supermarket. (Frozen products such as fish sticks are often made with Alaskan pollock, which is usually a safe bet; check the ingredients list to be sure.)

Buy a cookbook that can help."One Fish, Two Fish, Crawfish, Bluefish" (Smithsonian, 2003, $35) has recipes tailored to sensibly caught species from the likes of Emeril Lagasse and Rick Bayless.

Dine out at the right spots. Barton Seaver, 28, the much-buzzed-about chef of Hook in Georgetown, built his entire menu around sustainable seafood. Other options include Viridian and Restaurant Nora in the District, McGarvey's Saloon & Oyster Bar in Annapolis and Cafe Oggi in McLean.

Find options in the unlikeliest of places: Even the Filet-O-Fish at McDonald's is made with sustainably harvested Alaskan pollock. If a fast-food chain can do it, so can you.